Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$34.46	3.169%	$35.552	$35.55	$35.55	$35.60
Purchase #2	$75.87	8.459%	$82.2878	$82.29	$82.30	$82.30
Purchase #3	$45.86	4.218%	$47.7944	$47.79	$47.80	$47.80
Purchase #4	$81.69	10.675%	$90.4104	$90.41	$90.40	$90.40
Purchase #5	$32.89	6.107%	$34.8986	$34.90	$34.90	$34.90
Purchase #6	$189.50	5.568%	$200.0514	$200.05	$200.05	$200.10
Purchase #7	$244.40	8.607%	$265.4355	$265.44	$265.45	$265.40
7 purchase totals =	$704.67		$756.4301	$756.43	$756.45	$756.50